| IntrductionHuman immunodeficiency virus is the pathogen of acquired immunodeficiency syndrome. By now, HIV infection /AIDS cannot be cured completely or be prevented by any vaccine, because of the high variation rate of HIV gene. The gene variation of V3 loop in HIV envelop protein is associated with the cell tropism, replication dynamics, cytopathic activity and render HIV - 1 to escape from the attack of the immune system. It has been known that the HIV strains isolated from asymptomatic infectors were mainly macrophage tropic / non - syncyti-um - inducing strains, while the strains isolated from AIDS patients were always T - cell - lines tropic/ syncytium - inducing strains. The shift from M tropic/NSI phenotype to the T tropic /SI phenotype may have correlation to the rapid decline of the CD4+ T lymphocyte and the progression to AIDS. The gene variation of V3 loop was determined by the biological character of different strains, but the host immune competence and therapy may have important influence on the phenotype shift. So our subject aimed at the character of HIV - 1 V3 loop gene variation among HIV - 1 infected people in China and discussed the relationship between the gene variation and the disease progression, which might provide theory support for gene therapy, reasonable vaccine and disease progression observation.Materials and methodsCollected the whole blood sample of the HTV infectors and AIDSpatients in Liaoning province China and from which extracted the genome DNA. The HIV ?1 V3 and flanking region sequences were amplified by nested -PCR with env specific primers: ED5/ED12 in the first and ED31/ED33 in the second reaction. Products were purified with QIAquick Gel Extraction Kit and sequenced directly with primers ED31 by dideoxy chain termination method with sequenase ( USB) according to the manufacture . Grouped the HIV ?1 infectors according to the 2001 Chinese HIV infection /AIDS diagnostic standard-. AIDS group ( CD4 T cell < 200 × 10 /L) , asymptomatic infection group (CD4 T cell is 200×106/L). Downloaded HIV - 1 consensus sequence of different subtypes, aligned these sequence, computed genetic distance and drew the phylogenetic tree with BIOEDIT software package. Searched the mutation types and the positions among V3 loop, and compared them with the HIV - 1 strains epidemic all over the world. Computed the synonmous and non - synonmous substitutions and the ratio of them by SNAP software and compare the ds/dn difference between the AIDS group and the asymptomatic infection group. Statistics analyze with ranks sum test.Results1. The amino acid mutation of HIV -1V3 loop at HIV infection / AIDS group in ChinaIn AIDS group ,we could find at position 11 of V3 loop S to R , at position 13 H to S,T and N, at position 19 A to V, at position 20 F to Y, at position 25, 29 N to D , which were all usual mutations associated with T tropic /SI phenotype. The frequency of such amino acid mutations in specific positions was higher in AIDS group than that otthe asymptomatic infection group (P < 0. 05). On the opposite, we could find S at position 11 and D or Q at position 25 in all strains of the asymptomatic infection group, which were the characters of the M tropic /NSI phenotype. Of the most interest, we found some unusual tetramer composition on the tip of V3 loop: GQGR, APGR and RP-GA, GLGR, RPGA in addition to some rare mutation, such as; N to H at position 5 and H to S, F at position 34.2. The relationship between the CD4 absolute count and the immune pressure in different disease stageIn AIDS group, the CD4 positive T lymphocyte absolute count was(78±61. 4)×106/L, ratio of the synonymous and non - synonymous substitution was 1. 35±0. 42; while in the asymptomatic infection group , the CD4 positive T lymphocyte absolute count was (447 ±221. 7)×106/L, ratio of the synonymous and non - synonymous substitution was 1.25±0.45. Compared with the asymptomatic infection group , the ds/dn of the AIDS group showed some increasing tendency ,but did not reach s... |
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